• Title/Summary/Keyword: Pressure modulation

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압력제어솔레노이드밸브를 이용한 직접구동 방식의 유압회로에 의한 자동변속기의 변속품질 향상에 관한 연구

  • 김정관;한명철
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.577-580
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    • 1995
  • This paper suggests direct-acting hydraulic circuit to control clutches and brakes in automatic transmission. As only one pressure control valve controls the pressure of several friction elements with accumulators in conventional hydraulic circuit, the controllable range is limited. In addition, it is difficult to control the fine timing between apply clutch and release clutch. So, we designed new method to control the pressure of clutch which uses ressure control valve and pressure control solenoid valve independently in each friction element. through this structure improvement of hydraulic circuit, we can control the pressure of clutches and brakes finely and fine timing of between apply clutch and release clutch.

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Study on the Characteristics of Surge Pressure by High Frequency PWM Control in Braking System (제동장치에서 고주파수 PWM 제어에 의한 맥동특성 연구)

  • Kim, Byeong-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.3
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    • pp.109-114
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    • 2008
  • The solenoid valve of ABS hydraulic modulator is a two directional on-off valve and is controlled by around 100Hz on-off control. When the on-off valve is switched from open state to closed state, there are braking force deterioration, noise and vibration due to surge pressure in the wheel cylinder. In this study, identifies surge pressure in the braking process of ABS, and investigates the way to reduce the phenomenon. To reduce the surge pressure, PWM(Pulse Width Modulation) control with high frequency of 20kHz was attempted. In conclusion, by using the results of this study for the pressure surge prediction, we could expect enhancement of braking performance in ABS.

Pressure Control of Hydraulic Cylinder using high Speed On-Off Solenoid Valve (고속 온-오프 전자 밸브를 사용한 유압 실린더의 압력 제어)

  • 김상수
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.1
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    • pp.69-78
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    • 1999
  • In this study a new pattern of pressure control of hydraulic cylinder using high speed On-Off solenoid valve in the electro-hydraulic system has been suggested. The control valve is 3-way high speed On-Off solenoid valve which is operated by PWM(Pulse Width Modulation)control signal. The high speed On-Off solenoid valve has a tendency to induce severe pressure fluctuation in the hydraulic actuator so it has not been used for the purpose of closed loop control with direct pres-sure feedback. In this study closed loop control with direct pressure feedback is enabled by using a digital filter which has linear minimum mean square filter algorithm. Through some experiments it is confirmed that stable pressure control can be realized by the proposed control technique.

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Effects of frequency-amplitude modulation of silver spike point electrical stimulation on epinephrine and norepinephrine in human (인체에 적용한 주파수-진폭 변조 은-침점 전기자극이 Epinephrine과 Norepinephrine에 미치는 효과)

  • Choi, Young-Deog;Lim, Jong-Soo;Kim, Soon-Ja
    • Journal of Korean Physical Therapy Science
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    • v.7 no.2
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    • pp.567-577
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    • 2000
  • In human body, catecholamines, such as epinephrine and norepinephrine, can be increased anxiety, blood pressure and pain etc. The inhibitory effects of TENS, electroacupuncture and massage on the release of epinephrine, norepinephrine from sympathetic nerve endings has already been known. However, the effects of silver spike point stimulation on the catecholamines was not well understood. Therefore, the purpose of this study was to characterize the SSP-induced inhibitory effects of catecholamines. The following results were obtained. (1) The studies on urinary catecholamines released that the levels of epinephrine and norepinephrine of continue type SSP stimulation group were significantly lower than those in the control group in human in vivo. (2) The dose-response curves of epinephrine and norepinephrine in rat aortic smooth muscle strips were increased dose dependent manner respectively. However, the contractile response of norepinephrine in rat aortic smooth muscle strips were slightly differentiated. It is concluded that the SSP stimulation reflects to the inhibitory effects of epinephrine and norepinephrine in men. Especially, we believe that the amplitude-frequency modulation, such as continue type a)1d frequency modulation type, of SSP stimulation plays a role in regulating catecholamines.

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Spatial Complex Envelope of Acoustic Field : Its Definition and Characteristics (음장의 공간 복소 포락: 정의와 특성)

  • Park, Choon-Su;Kim, Yang-Hann
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.8
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    • pp.693-700
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    • 2007
  • We can predict spatial acoustic pressure distribution on the plane of interest by using acoustic holography. However, the information embedded in the distribution plot is usually much more than what we need: for example, source locations and their overall propagation pattern. One possible candidate to solve the problem is complex envelope analysis. Complex envelope analysis extracts slowly-varying envelope signal from a band signal. We have attempted to extend this method to space domain so that we can have spatial information that we need. We have to modulate two dimensional data for obtaining spatial envelope. Although spatial modulation basically follows the same concept that is used in time domain, the algorithm for the spatial modulation turns out to be different from temporal modulation. We briefly describe temporal complex envelope analysis and extend it to spatial envelope of 2-D acoustic field by introducing geometric transformation. In the end, the results of applying the spatial envelope to the holography are envisaged and verified.

Fiber-Optic Sensor for Acoustic Waves (광섬유를 이용한 음파탐지기의 제작)

  • 유회준;이경목;황준암
    • Proceedings of the Korean Institute of Communication Sciences Conference
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    • 1983.10a
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    • pp.44-47
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    • 1983
  • Through intensity modulation induced by micro bending of an optical fiber, a sensor detects the pressure and frequency of acoustic wave has been implemented. Axial slots on the cylinder suface with a period of 5.5 mm induce efficient microbending of the fiber, and a rubber sleeve covering the fiber enhances the fiber. Compared with a conventional hydrophone, it has a low minimum detectable pressure and can detect acoustic wave in 100Hz - 2KHz range.

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Effects of Modulation Type on Electrically-Elicited Tactile Sensation (전기자극 변조방식이 체성감각에 미치는 영향)

  • Hwang, Sun-Hee;Ara, Jawshan;Song, Tong-Jin;Bae, Tae-Sue;Park, Sang-Hyuk;Khang, Gon
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.7
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    • pp.711-716
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    • 2012
  • The purpose of this study was to investigate how the modulation method affects the effectiveness of eliciting tactile sensations by electrical stimulation. Two methods were employed and the results were compared and analyzed; pulse amplitude modulation (PAM) and pulse width modulation (PWM). Thirty-five healthy subjects participated in the experiments to measure the stimulation intensity that began to elicit a tactile sensation - activation threshold (AT). Constant-current monophasic rectangular pulse trains were employed, and the stimulation intensity was varied from zero until the subject felt any uncomfortable sensation. The step size of the stimulation intensity was 100nC/pulse. After each experiment, the subject described the sensation both quantitatively and qualitatively. The two modulation methods did not make a significant difference as far as the AT values were concerned, but most of the subjects showed 'intra-individual' consistency. Also, it was confirmed that our range of the stimulation parameters enabled us to obtain three major tactile sensations; tickling, pressure and vibration. The results suggested that the stimulation parameters and the modulation type should be selected for each individual and that selective electrical stimulation of the mechanoreceptors needs more diversified researches on the electrode design, multi-channel stimulation protocol, waveforms of the pulse train, etc.